Background. Sinonasal mucosal melanoma (SNMM) is a rare entity originating from melanocytes of the sinonasal mucosa. Postoperative radiotherapy is recommended in all cases to increase local control. However, external radiotherapy is rarely used as a definitive treatment modality. In this report, we present 4 cases of SNMM treated with CyberKnife (Accuray, Sunnyvale, CA).